6 Hydrangea Facts That Even Expert Gardeners Don’t Know

Jill StaakeUpdated: Jun. 05, 2023

Hydrangeas are classic garden shrubs but, as these fascinating facts prove, they're more complex than you may think.

Hydrangea Facts: Not All Hydrangeas Are the Same

Invincibelle Ruby hydrangea features bright pink mophead flowers. — Invincibelle Ruby smooth hydrangea features bright pink mophead flowers.

Hundreds of hydrangea species and cultivar exist, but there are a few common types. Each type has different attributes that you need to consider. Read more hydrangea facts below and check out our overview to pick out the best hydrangea species for your yard.

Look for these six at the garden center:

Bigleaf (also called French hydrangea)
Oakleaf
Panicle
Smooth
Mountain
Climbing

Only Some Hydrangeas Change Colors

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Hydrangeas are known for their ability to transition between pink or blue colors, but not all types change their hues. Bigleaf hydrangeas that can change color are blue when the soil pH is below 5.5 and pink when the pH is 6.0 or higher. Learn how to change the color of your hydrangea.

Hydrangeas Can Handle the Cold

Fire Light panicle hydrangea features pink and white flower clusters.

Panicle hydrangeas are incredibly cold tolerant. Varieties of these tough plants grow well in zone 3, which covers the coldest areas of the continental United States. They’re versatile enough to grow in the heat of the Deep South, too.

Did you know—cold temperatures can cause some hydrangeas to not bloom.

How Tall Do Hydrangeas Grow?

A close-up of a purple hydrangea bloom that's shaped like a flower. — A close-up of a purple hydrangea bloom that’s shaped like a heart

Hydrangeas come in a variety of sizes. Some hydrangeas are small enough to fit in containers, but other plants like climbing hydrangeas can reach 30 feet or even taller with the right growing conditions and support.

Use our guide to learn how to care for hydrangeas so they reach their full height.

Bigleaf Hydrangeas Have Two Kinds of Flowers

A closeup of Lets Dance Sky View Hydrangea, which features large pink and green flower clusters. — Let’s Dance Sky View bigleaf hydrangea features large pink and green flower clusters.

Bigleaf, or French hydrangeas, are the most common type you might see in a backyard. But they may be tricky to identify because they can have two different styles of flowers. They also need to be pruned at the right time to get them to bloom.

The first kind of bloom is large, showy and called a mophead. Lacecaps are the other type, which have tiny budlike florets surrounded by larger blooms.

One Hydrangea Is a State Wildflower

Pwgatsbypinkoakleafhydrangea — Gatsby pink oakleaf hydrangea

You might not see these plants growing alongside the road or in a meadow, but in 1999, Alabama designated the oakleaf hydrangea as its state wildflower.

Next, discover the gorgeous ‘Wee Bit Giddy’ hydrangea.